In my case the reason the error happened was a
bit confusing. But it came down to this. That IP address got set to my
public IP address in my hotel. When I went to present I didn't have a
network connection, and so that address was no longer present. The easiest fix for this when using the emulator is to set that Default Debug Host IP to the gateway of your VMWare's NAT setup.

I don't have an easy was of getting that, but the way I did it was:Determine IP address for Playbook emulatorBlackBerry SettingsAbout ->inet

For me 192.168.253.138.

Determine all of my system's IP addressesOSX ifconfigWindows ipconfig

When I did that, I found one address (192.168.253.1) that was a reasonable bet for the gateway of the NAT network.